Observation instruments such as endoscopes are used in medical and other applications to allow a visual inspection of locations which are not readily accessible. For example, endoscopes are used in medical applications to provide a view of an area within a patient's body. An endoscope typically includes an elongated shaft of relatively small diameter extending from a handle to a distal end. An imaging or viewing arrangement is included with the endoscope to allow a user to obtain a view from the distal end. Particularly in early endoscopes this arrangement included a system of lenses and a light conduit through the shaft to direct an image from the distal end to an eyepiece associated with the endoscope handle. In many modern endoscopes, the imaging or viewing arrangement includes an electronic imaging device mounted in a distal head at the distal end of the endoscope. Such an electronic imaging device collects image data and communicates that data through the shaft and handle ultimately to a processing system that assembles the data into an image to be displayed on a suitable display device.
To provide the desired illumination for the image to be collected, light may be generated by a light source at the endoscope handle and directed through suitable conduits in the shaft (such as optical fibers for example) to the endoscope distal head where the light can be directed as desired through suitable lenses. Alternatively to relying on light conducted through the shaft to the distal end of the endoscope, a suitable light source such as an LED lamp may be placed at the distal head of the endoscope together with the electronic imaging device to provide the required illumination.
In addition to the imaging or viewing arrangement and the illumination arrangement, some endoscopes and similar instruments include a working channel which extends from the instrument handle through the elongated shaft to the distal head. This working channel comprises a passageway through which fluids may be introduced into the area under observation during the endoscopic procedure, or through which a suction may be applied. The working channel may also be used to insert tools into the area under observation for performing certain functions in the course of the endoscopic procedure.
Although it is desirable or necessary to provide room in the distal head of the observation instrument for the imaging or viewing arrangement, illumination arrangement, and working channel, the distal head of the instrument must have a cross-sectional dimension that remains as small as possible in order to facilitate the desired observation and other procedures intended for the instrument. This is true for all applications, but especially for medical applications. This requirement for a small cross-sectional dimension limits the electronic imaging devices which may be used in an observation instrument. In particular, some image sensors are too wide to orient with their image collecting surface parallel to the end of the distal head where the image is to be collected.
U.S. Pat. Nos. 4,741,327 and 5,454,366 each show an endoscope with an imaging device oriented in a plane essentially parallel to the longitudinal axis of the endoscope head. In each case a prism is employed to direct the image from the objective lenses of the device to the imaging device. However, the configurations shown in these two patents are relatively long, leave less room for other components of the distal head, and have other disadvantages.
There remains a need for image sensor arrangements which can be mounted at the distal head of an observation instrument such as an endoscopic device without taking up too much room or requiring a larger distal head.